Download - THE WIMPLESS MIRACLE
THE WIMPLESSMIRACLEJonathan Feng, UC Irvine
6 June 2008, Anticipating the LHC, KITP Santa Barbara
Based on Feng and Kumar, arXiv:0803.4196, and work in progress with
Jason Kumar Louie Strigari Huitzu Tu Haibo Yu
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LHC EXPECTATIONS
2 reasons to anticipate something rather than nothing (beyond the Higgs):
• Gauge hierarchy problem
• Dark matter– Qualitative: Ockham’s razor– Quantitative: WIMPs give the right thermal relic density– Less robust: Other production mechanisms, candidates possible– More robust: Independent of notions of naturalness
WIMPs motivate many experimental searches– Colliders: missing energy– Dark matter searches: focused on masses around mW ~ 100 GeV
Xerxes Tata’s talk
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START OVER
• What do we really know about dark matter? – All solid evidence is gravitational– Also solid evidence against strong and EM interactions
• A reasonable 1st guess: dark matter has no SM gauge interactions, i.e., it is hidden
• Hidden sectors: distinguished history and recent interestLee, Yang (1956); Gross, Harvey, Martinec, Rohm (1985)
Schabinger, Wells (2005); Patt, Wilczek (2006); Strassler, Zurek (2006); Georgi (2007); Kang, Luty (2008)
March-Russell, West, Cumberbatch, Hooper (2008); McDonald, Sahu (2008); Kim, Lee, Shin (2008); Krolikowski (2008); Foot
(2008); many others
• What one (seemingly) loses– The WIMP miracle
– Predictivity– Non-gravitational signals
THE WIMP MIRACLE
• WIMPs naturally freeze out with the desired relic density
• More explicitly:
(gX, mX) ~ (gW, mW) X ~ DM
• Note: X , not nX, appears above; mX enters through and dimensional analysis
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Kolb, Turner (1990)
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HIDDEN SECTORS
• Can we obtain something like the WIMP miracle, but with hidden DM? Need some structure.
• Consider standard GMSB with one or more hidden sectors
• Each hidden sector has its own gauge groups and couplings
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• Particle Physics
Superpartner masses, interaction strengths depend on gauge couplings
• Cosmology
depends only on the SUSY Breaking sector:
X ~ WIMP ~ DM
Any hidden particle with mass ~ mX will have the right thermal relic density (for any mX)
THE WIMPLESS MIRACLEFeng, Kumar (2008)
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• The thermal relic density constrains only one combination of gX and mX
• These models map out the remaining degree of freedom
• This framework decouples the WIMP miracle from WIMPs, gives a new class of candidates with WIMP pedigree, but with a range of masses/couplings, e.g.:
WIMPLESS DARK MATTER
mX
gX
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• This requires that an mX particle be stable. Can one be?
STABILITY
MSSM
mX sparticles, W, Z, t q, l 0 p, e, , , G̃�
Flavor-free MSSMO(1) Yukawas
mX sparticles, W, Z, q, l, �or
0 g, , , G̃�
• If the hidden sector is a flavor-free MSSM, a natural NLSP candidate, the stau (or tau), would be stabilized by charge conservation. No bounds from hidden sea water, etc.
AN ASIDE: SUSY FLAVORAND DARK MATTER
• Generically in SUSY there is tension between flavor and dark matter solutions– Flavor: small gravity effects light gravitino– DM: neutralino LSP heavy gravitino
• The standard thermal gravitino is no longer viable
– GL h2 ≈ 1.2 (mGL / keV) Pagels, Primack (1982)
– mGL > 2 keV; DM can’t be too hot Viel et al.; Seljak et al. (2006)
• WIMPless DM provides one resolution (there are others)
Han, Hempfling (1997); Baltz, Murayama (2003); Ibe, Kitano (2006); Feng, Smith, Takayama (2007)
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CONCRETE MODELS
• Does all of this hold up under closer scrutiny?
• What hidden sectors are viable?
BBN: N = 3.24 ± 1.2
Cyburt et al. (2004)
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• Possible resolutions
– Model building: g*H < g*MSSM
– Cosmology: Hidden = MSSM or similar, but hidden sector reheats to lower temperature
TH = TMSSM
Feng, Tu, Yu (2008)
RELIC DENSITIES IN COLDER HIDDEN SECTORS
• The hidden Boltzmann equation:
– All sectors contribute to H
– <v> thermally-averaged over TH
• Consider a hidden sector with– flavor-free MSSM– 1 generation– L WIMPless candidate– L L , Z (all are hidden particles)
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• Minimal impact : <v> = 0 + 1 v2 + …, low T only suppresses sub-dominant P-wave contributions
Y
Feng, Tu, Yu (2008)
TH = TMSSM
RELIC DENSITIES IN COLDER HIDDEN SECTORS
• Numerically solve hidden Boltzmann equation for various (gX, mX)
• The parameters that give the correct relic density are also those that give weak-scale MSSM masses.
• The dimensional analysis is confirmed in this concrete example
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TH = 0.5 TMSSM
Feng, Tu, Yu (2008)
DETECTION
• So far, WIMPless DM has no observable consequences (other than gravitational)
• But we can add connectors with both MSSM and hidden charges; e.g., bifundamentals motivated by intersecting brane models
• Y particles mediate both annihilation to and scattering with MSSM particles
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X
X
f
fY
Feng, Kumar, Strigari (2008)
EXAMPLE• Suppose the connectors are chiral Y multiplets, interacting through
• Y particles get mass from both MSSM and hidden gauge-mediation, so
mY ~ max (mW, mX)
• Does annihilation through Y’s destroy the relic density properties?
No, annihilation to MSSM is subdominant, as long as f < gW.
• Y’s are subject to 4th generation constraints from collider direct searches, precision electroweak, Yukawa perturbativity. For 4th generation quarks,
250 GeV < mY < 500 GeV
Kribs, Plehn, Spannowsky, Tait (2007); Fok, Kribs (2008)
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SIGNATURES
• DM is under investigation in ~100 experiments around the world. Many hints of DM have been reported– DAMA– HEAT– HESS– INTEGRAL– WMAP haze– …
• Most are not naturally explained by WIMPs. What about WIMPless DM?
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DIRECT DETECTION
• WIMPless DM can have very large cross sections, and masses from MeV to 10 TeV, explain DAMA
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u contours; mY = 400 GeV
Gelmini, Gondolo (2005); TEXONO (2007)
INDIRECT DETECTION
• WIMPless DM predicts constant for all m
• But n ~ 1/m, and so indirect rates ~ n2 are greatly enhanced for light DM (annihilation cross sections are determined by , not g)
• GLAST will be sensitive to ~GeV to 10 GeV WIMPless DM, even for smooth halos with JV ~ 1 (not so for WIMPs)
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LHC SIGNALS• The WIMPless DM scenario motivates unusual LHC phenomenology
of GMSB + 4th generation. Many effects:
– Conventional GMSB spectrum with GMSB signals (prompt photon, multi-leptons, etc.)
– But also pair production YY XX f f, “gravity-mediated” missing energy signal
– Higgs mass as high as 300 GeV– gg h enhanced by ~ 10 from 4th generation in loop– Higgs portal– Enhanced, viable electroweak baryogenesis
Kribs, Plehn, Spannowsky, Tait (2007); Fok, Kribs (2008)
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SUMMARY
• Early days
• WIMPless dark matter– Relic density: ~ 0.1– Mass: MeV to 10 TeV– Hidden gauge couplings: 10-3 to 1
• WIMP pedigree with potential for new signals– Direct detection– Indirect detection– LHC– Cosmology
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